Herein, we report a new case of Danon's disease in a 41-year-old Frenchman. This patient displays the typical clinical triad, with cardiomyopathy, mental retardation and myopathy, and a vacuolar myopathy without acid alpha-glucosidase deficiency. He has also developed a diffuse chorio-capillary ocular atrophy, and represents the second case of successful heart transplantation in this lysosomal disease. Interestingly, analysis of LAMP-2 protein expression in cultured fibroblasts revealed a primary deficiency of this lysosomal membrane protein. This defect resulted from a yet undescribed deletion in exon 7 of lamp-2 gene.